Any of you bassists out there using an echo box of any kind? If so, which one? And when? And why? Just for solos, or within the context of a song?

Not me, but Justin Chancellor has proved to be an absolute beast with his, particularly in the way he's managed to work it in on TOOL's "10,000 Days" and "Lateralus" albums.

I have a friend back home that plays through a reverse delay pedal. he plays in an alternative band and only uses it when the band is having a "far out" moment, which they tend to have quite a bit;)

I'm not sure what it is but it makes some wild sounds.

Well, if you're talking about the "reverse guitar" on Beatles or Hendrix records, that was done by actually playing the recorded guitar part, on tape, backwards through the recorder. A reverse delay probably uses some kind o digital trickery to take what you play, then reverse it digitally very quickly before letting it "get out" of the pedal. To pply a guitar part "in reverse," I Think you'd have to seriously plan it out so that it would fit harmonically with the chord structure.

There's band called "Explosions in the Sky" that does a lot of freaky atmospheric music with massive delay, echo, phasing and all the other things your guitar teacher told you not to use.

This is actually a reverse delay pedal. I'm not sure how they work but it is definitely digital. It may send the signal through and then back through very quickly. My giga delay has a reverse setting. Not sure if it is truly a reverse delay but it makes some sounds that I don't think I will ever use.